My feelings concerning sabots and their slugs are if you're going to use them, use the largest bullet possible - closest to bore size, thinnest sabot.

The Lyman sabot slug that uses ordinary trap or field petal'd wads might be the best. My own testing of them got put on hold, but perhaps I can get around to them now that spring is here - we think. HA! - still a couple feet of snow in the bush.

Ed Hubel says the guys are reporting good accuracy with the Lymans slugs from rifled barrels and pretty good from smooth as well.

In 12 bore, they run 14 bore in size, ie: .690". They can also be case of straight WW metal. The ones I have are 506gr. instead of 525gr., their pure lead weight.

I think the 20 bore size runs around 385gr. Because the blocks are iron, they can be chucked up in a 4 jaw and easily altered in shape or the plunger could be altered with a simply file, to make the blocks cast a solid bullet or make a different shaped plunger, increasing their weight to whatever is desired.